A 2-order MIMO full-duplex antenna system

The paper presents an antenna system with combined full-duplex and 2-order multiple-input-multiple-output (MIMO) functionalities, i.e., a system capable of spatially multiplexing and spatially demultiplexing 2 datastreams in the same frequency and in the same time. By exploiting symmetries in the construct and the feed, simple corrective beamforming weights can be applied at the transmitter (Tx) ports in order to selectively cancel the Tx signal at the receiver (Rx) ports, thus guaranteeing a large amount of isolation necessary for full-duplex (i.e., simultaneous and in-band Tx and Rx) operation. On the other hand, the 2 MIMO ports (either at the Tx or at the Rx) are sufficiently decoupled thanks to polarization diversity. The proposed antenna system exhibits a remarkable level of full-duplex isolation over a wide bandwidth while maintaining low coupling between its MIMO ports and can serve as a concrete implementation of an antenna system equipped with both MIMO as well as full-duplex capabilities.